faceids-roi.ts

const ROI_BORDER_RATIO = 0.01;

interface IFaceDetect {
  detectId: string;
  bbox: { left: number; top: number; right: number; bottom: number };
  detectionScore: number;
  lowQuality: boolean;
}

interface IBbox {
  left: number;
  top: number;
  right: number;
  bottom: number;
}

interface IDrawingFaces {
  bbox: IBbox;
}

const compareFaces = <T extends IDrawingFaces>(aFace: T, bFace?: T): T => {
  if (!bFace) {
    return aFace;
  }
  const a = aFace.bbox;
  const b = bFace.bbox;

  const aw = Math.abs(a.right - a.left);
  const ah = Math.abs(a.bottom - a.top);
  const bw = Math.abs(b.right - b.left);
  const bh = Math.abs(b.bottom - b.top);

  if (aw + ah > bw + bh) {
    return aFace;
  }
  return bFace;
};

const getBiggestFace = <T extends IDrawingFaces = IDrawingFaces>(
  faces: T[]
): T | null => {
  if (!faces.length) {
    return null;
  }
  return faces.reduce(compareFaces);
};

const calcRoi = (height: number, width: number): IBbox => {
  const left = Math.floor(width * ROI_BORDER_RATIO);
  const top = Math.floor(height * ROI_BORDER_RATIO);
  const roiWidth = Math.ceil(width * (1 - 2 * ROI_BORDER_RATIO));
  const roiHeight = Math.ceil(height * (1 - 2 * ROI_BORDER_RATIO));
  return {
    left,
    top,
    right: left + roiWidth,
    bottom: top + roiHeight
  };
};

const checkRoi = (rect: IBbox, roi: IBbox) => {

    const rectLeft = rect.left;
    const rectTop = rect.top;
    const rectRight = rect.right;
    const rectBottom = rect.bottom;

    const roiLeft = roi.left;
    const roiTop = roi.top;
    const roiRight = roi.right;
    const roiBottom = roi.bottom;

    return (
        rectLeft >= roiLeft &&
        rectTop >= roiTop &&
        rectRight <= roiRight &&
        rectBottom <= roiBottom
    );
}

// ...

const detection: IFaceDetect[] =
  await faceids.faceIdsGlobalService.detectFaceByBlob({
    ...this.contextService.context,
    data: {
      blob,
    },
  });

const biggestFace = getBiggestFace(detection.data);
const roi = calcRoi(image.naturalHeight, image.naturalWidth);

if (!biggestFace) {
  return false;
}

if (!checkRoi(biggestFace.bbox, roi)) {
  return false;
}

return true;